BUTLER TWP — The Pennsylvania Department of Transportation in Butler County is changing its procedure for plowing bridges following an accident in which snow and ice pushed off a bridge by a plow truck struck a vehicle on the road below. “Basically, we’re going to be more cautious,” said PennDOT county manager Bob Skrak. Skrak told crews that if there is already snow on the walls and sides of bridges, they should let it build up rather than try to push it off the bridge. After every heavy snow, PennDOT will assess bridge decks in the county. If a bridge is found to have too much snow against its walls, crews will use a front loader to clear it. Flaggers will stop traffic on roads below while the work is being done. Skrak noted that in counties such as Erie and Crawford, where heavy snow falls more often, PennDOT has similar procedures in place. “There’s a potential for serious injury, and it’s obviously something we want to prevent,” Skrak said. The accident happened Dec. 29 on an overpass that carries Route 19 over Route 422 in Muddy Creek Township. At about 12:50 p.m., Larry A. Byler of Jacksonville, Fla., was driving eastbound on Route 422 when snow and ice plowed by a PennDOT truck on Route 19 fell on his vehicle, shattering the windshield on him and passenger Eric Williams of Philadelphia, Miss. Both sustained minor injuries. Three other passengers were not injured. The driver of the plow will not be disciplined. Skrak said the driver was working safely, traveling at a low rate of speed and did not know that his plow caused the accident. When the driver saw the damaged vehicle, he stopped to help.